Fogged direct-positive silver halide emulsions containing triazolium salts and the use thereof in reversal processes

ABSTRACT

FOGGED, DIRECT-POSITIVE, SILVER HALIDE EMULSIONS CAN BE DEVELOPED IN THE PRESENCE OF TRIAZOLIUM SALTS TO PRODUCE IMPROVED PHOTOGRAPHIC PROPERTIES. IN ONE EMBODIMENT, BISTRIAZOLIUM SALTS ARE INCORPORATED IN AT LEAST ONE LAYER OF THE DIRECT-POSITIVE ELEMENT AND REDUCED DICHROIC FOG IS OBSERVED UPON DEVELOPMENT, ESPECIALLY WHEN THE DEVELOPER CONTAINS HIGH HALIDE-ION CONCENTRATIONS.

United States Patent US. C]. 96-64 R 11 Claims ABSTRACT OF THE DISCLOSURE Fogged, direct-positive, silver halide emulsions can be developed in the presence of triazolium salts to produce improved photographic properties. In one embodiment, bistriazolium salts are incorporated in at least one layer of the direct-positive element and reduced dichroic fog is observed upon development, especially when the developer contains high halide-ion concentrations.

This is a continuation-in-part application of US. application Ser. No. 68,503 of Glen M. Dappen, filed Aug. 31, 1970, now abandoned.

This invention relates to improved fogged, direct-positive emulsions and to improved processes of developing fogged, direct-positive, silver halide emulsions. In one aspect, this invention relates to direct-positive elements comprising (1) a support, (2) at least one layer thereon containing a fogged, direct-positive, silver halide composition and (3) at least one layer containing a triazolium salt. In another aspect, this invention relates to processes for developing direct-positive photographic elements in the presence of a silver halide developer composition comprising halide ions and a triazolium salt.

It is known in the art to develop fogged, direct-positive, silver halide compositions in developing compositions containing a high level of halide ions. However, as the developer solution becomes extensively used, the formation of a yellow fog, often referred to as dichroic fog, becomes prevalent in the developed image record. The consistency of results can be improved by the addition of nitron to the silver halide emulsion, but further improvements in controlling the dichroic fog are desirable.

I have now found that when fogged, direct-positive, silver halide emulsions are developed in the presence of a triazolium salt and especially the bis-triazolium salts, the image record exhibits improved photographic properties such as, for example, substantially reduced dichroic fog, especially when the developer contains high halide-ion concentrations. This reduction in dichroic fog is quite unexpected since similar compounds, such as nitron, do not provide the same improvements as the triazolium salts.

'In one embodiment according to this invention, bis-triazolium salts are incorporated in at least one layer of the photographic element.

In a highly preferred embodiment, the bis-triazolium salt is a 1,10-dithiadecamethylene bis-3-(l,4-diphenyl-1, 2,4-triazolium paratoluene sulfonate).

In another preferred embodiment of this invention, the developers used to process the fogged, direct-positive elements contain at least 0.5 g./liter of a-halide.

The triazolium salts used in accordance with this invention can be present in the developing composition during the processing step, but are preferably present in the photographic element itself in the silver halide-containing layer or in adjacent layers. Generally, the direct-positive element comprises from about 1x10 moles to about 1 10 moles, and preferably from about 1 10 moles to about 5X moles, of the triazolium salt per mole of silver. When used in the developing composition, it is generally used at a concentration of 5X10 moles per liter to about 5 10 moles per liter.

3,740,226 Patented June 19, 1973 In one preferred embodiment of this invention, the triazolium salts are bis-triazolium salts of the formula:

LL E

1 1 X in X wherein R R R and R are alkyl groups having from 1 to 10 carbon atoms or are preferably aryl or aralkyl groups containing from 5 to 12 carbon atoms; R is an alkylene group having from 1 to 15 carbon atoms and preferably comprises from 6-12 carbon atoms; Q is a sulfur atom, an oxygen atom or a nitrogen atom, but is preferably a sulfur atom; and X is an anion such as paratoluene sulfonate, etc. Typical compounds of this type include 1,10dithiadecamethylene bis-3-(l,4-dipheny1-1,2,4- triazolium paratoluene sulfonate) and the like.

In another preferred embodiment, the triazolium salts are bis-triazolium salts represented by the formula:

wherein R R and R are as mentioned above and R and R can each be an aryl or aralkyl group of from 5 to 12 carbon atoms. Typical useful compounds of this type include 3,3'(N,N decamethylene diani1ino)bis(1,4-di phenyl-1,2,4-triazolium)tosylate and the like.

In another embodiment, inner triazolium salts are used in the fogged, direct-positive elements of this invention. Typical useful inner salts are 3-hydroxy-l,4-diphenylpseudo-1,2,4-triazole and the like.

Typical useful direct-positive systems which can be made using the improvements of this invention include:

(1) Emulsions containing fogged silver halide grains which have internal centers for the deposition of photolytic silver such as those generally disclosed in Berriman, US. Pat. 3,367,778 issued Feb. 6, 1968, including emulsions comprising grains which have centers which promote the deposition of silver which are either sufiiciently small or sufiiciently buried within the crystal as to be not accessible to initiate surface development to a visible image. Silver halide grains of this latter type can be provided by using very low concentrations of metal dopants or sensitizing agents throughout the precipitation, or adding the metal dopant to the precipitation medium during the initial part of the precipitation.

2) Emulsions which contain silver halide grains which are uniformly fogged to specific levels and contain electron-accepting compounds adjacent the grains, as described in Illingsworth, US. Pat. 3,501,305 issued Mar. 17, 1970.

(3) Emulsions comprising fogged regular grains which contain an electron-accepting compound or desensitizer adjacent the grains as described in Illingsworth, US. Pat. 3,501,306 issued Mar. 17, 1970.

(4) Emulsions comprising monodispersed grains which have been reduction and gold fogged as described in Illingsworth, US. Pat. 3,501,307 issued Mar. 17, 1970.

The silver halides employed in the preparation of the photographic compositions described herein include any of the photographic silver halides as exemplified by silver bromide, silver chloride, silver chlorobromide, silver bromoiodide, silver chlorobromide, and the like. Silver halide grains having a mean grain diameter, i.e., an average grain size in the range of about .01 to about 2 microns, preferably about .02 to about 1 micron, give particularly good results in reversal systems. The silver halide grains can be any suitable shape such as cubic or octahedral, but they are preferably cubic, and more preferably cubicregular. The preferred photographic silver halide emulsions comprise at least 50 mole percent bromide, the most preferred emulsions being silver bromoiodide emulsions, particularly those containing less than about mole percent iodide. The photographic silver halides are generally coated at silver coverages in the range of about 50 to about 500 milligrams of silver per square foot of support.

The direct-positive photographic silver halide emulsions made in accordance with this invention contain silver halide grains which are fogged. Fogging can be elfected by chemically or physically treating the photographic silver halides by methods previously described in the prior art. Such fogging can be accomplished by various techniques such as chemical sensitization to fog, particularly good results being obtained with techniques of the type described by Antoine Hautot and Henri Saubenier in Science et Industries Photo graphiques, Vol. XXVIII, January 1957, pages 57-65. The silver halide grains can be fogged with the high-intensity light, reduction fogged with a reducing agent such as thiourea dioxide or stannous chloride or fogged with gold or noble-metal com pounds. Combinations of reduction fogging agents with gold compounds or compounds of another metal more electropositive than silver, e.g., rhodium, platinum or iridium, can be used in fogging the silver halide grains. The fogged silver halide grains in the direct-positive photographic emulsions of this invention give a density of at least 0.5 when developed without exposure for 5 minutes at 68 F. in Kodak DK-SO developer when a direct-positive emulsion containing such grains is coated at a coverage of 50 to about 500 mg. of silver per square foot of support.

The direct-positive photographic emulsions of this invention can comprise reduction and gold fogged silver halide grains, i.e., silver halide grains which are fogged with a combination of a reduction fogging agent and a gold fogging agent. The use of low concentrations of reduction and gold fogging agents in such a combination give unique fogged silver halide grains which are characterized by a rapid loss of fog upon chemical bleaching. It is known that 1 equivalent weight of a reducing agent will reduce 1 equivalent weight of silver halide to silver. To obtain the fogged silver halide grains which are characterized by a rapid loss of fog upon bleaching, much less than 1 equivalent weight of reduction fogging agent is employed. Thus, less than about 0.06 milliequivalent of reduction fogging agent per mole of silver halide is employed in fogging the silver halide grains. Generally, about 0.00025 to about 0.06, preferably about 0.0005 to about 0.03 milliequivalent of reduction fogging agent per mole of silver halide is employed in fogging the silver halide grains in the practice of this invention. Higher concentrations of reduction fogging agent can result in a substantial loss in photographic speed. A preferred reduction fogging agent employed in combination with the gold fogging agent, or a compound of another metal more electropositive than silver, is thiourea dioxide which is preferably employed in a concentration in the range of about 0.01 to about 3, most preferably about 0.05 to about 2, mg. per mole of silver halide or about 0.001 to about 0.03 millimole per mole of silver halide. Stannous chloride is another suitable reduction fogging agent which is used in practicing this invention and is preferably used in concentrations in the range of about 0.05 to about 3 mg. of stannous chloride per mole of silver halide. The use of the reduction and gold fogging agents in low concentration gives direct-positive photographic silver halide emulsions exhibiting outstanding photographic speed. Examples of suitable reduction fogging agents which can be employed in the practice of this invention include hydrazine, phosphonium salts such as tetra-(hydroxy methyl)phosphonium chloride, thiourea dioxide as disclosed in U.S. Pats. 3,062,651 by Hillson issued Nov. 6, 1962, and 2,983,609 by Allen et al. issued May 9, 1961, reducing agents such as the stannous salts, e.g., stannous chloride, as disclosed in U.S. Pat. 2,487,850 by Carroll issued Nov. 15, 1939, polyamines such as diethylene triamine as disclosed in U.S. Pat. 2,519,698 by Lowe et al. issued Aug. 15, 1950, polyamines such as spermine as disclosed in U.S. Pat. 2,521,925 by Lowe et al. issued Sept. 12, 1950, bis(B-amino-ethyl) sulfide and its water-soluble salts as disclosed in U.S. Pat. 2,521,926 by Lowe et al. issued Sept. 12, 1950, and the like.

The gold fogging agents employed in practicing this invention can be any gold salt suitable for use in fogging photographic silver halide grains and includes the gold salts disclosed in U.S. Pat. 2,399,083 by Waller et al., issued Apr. 23, 1946, and 2,642,361 by Damschroder et al. issued June 16, 1953. Specific examples of gold fogging agents are potassium chloroaurite, alkali metal aurous thiosulfates, aurous sulfide, potassium aurithiocyanate, potassium chloroaurate, auric trichloride, Z-aurosulfobenzothiazole metho chloride, and the like. The concentration of gold fogging agent employed in the practice of this invention is subject to variation, but is generally in the range of about 0.001 to about 0.01 millimole per mole of silver halide. Potassium chloroaurate is a preferred gold fogging agent and is often used at concentrations of less than about 5 mg. per mole of silver halide and preferably at concentrations in the range of about 0.5 to about 4 mg. per mole of silver halide.

Preferably, the direct-positive emulsions used in this invention contain electron-accepting compounds, often referred to as desensitizers or electron traps, which are generally compounds having an anodic polarographic halfwave potential and a cathodic polarographic potential which, when added together, give a positive sum. Typical useful electron-accepting compounds, along with methods of determining the polarographic potentials, are disclosed in the above-mentioned applications on direct-positive emulsions, as well as in Illingsworth et al., U.S. Pat. 3,501,310 issued Mar. 17, 1970. An especially useful class of electron acceptors which can be used in the directpositive photographic silver halide emulsions and processes of this invention are cyanine dyes such as the imidazo[4,5-b]quinoxaline dyes. Dyes of this class are described in Brooker and Van Lare, U.S. Pat. 3,431,111 issued Mar. 4, 1969. In these dyes, the imidaZo[4,5-b] quinoxaline nucleus is attached, through the 2-carbon atom thereof, to the methine chain.

The direct-positive emulsions of this invention also can contain compounds referred to as halogen-accepting or halogen-conducting compounds, especially if the halide of the emulsion is a high-chloride emulsion. Useful compounds of this type are generally characterized by an anodic polarographic potential less than 0.85 and a cathodic polarographic potential which is more negative than -1.0. Highly preferred species of compounds of this type are merocyanine dyes having the above halfwave potentials. Typical compounds of this type, along with methods of determining the polarographic potential, are disclosed in the above-mentioned applications on direct-positive emulsions as well as in Wise, U.S. Ser. No. 615,360 filed Feb. 13, 1967.

The invention can be further illustrated by the fol lowing examples of preferred embodiments thereof.

EXAMPLE 1 Preparation of 1,10-dithiadecamethylene bis-3-(1,4- diphenyl-1,2,4-triazolium paratoluene sulfonate) Dissolved in 10 ml. of hot butyl alcohol is 2.1 g. of anhydro-3-mercapto 1,4 diphenyl 1,2,4 triazolium hydroxide. A separate solution containing 4.0 g. decamethylene-di-p-toluenesulfonate in 10 ml. of hot butyl alcohol is added to the above triazolium solution and boiled for 10 minutes until the combined 20-ml. solution is reduced to 10 ml. Then the solution is heated for 1 hour on a steam bath and chilled. A white precipitate is ob tained when 50 ml. of ether is added to the cooled solution. The crude yield of 3.6 g. is purified by recrystallization with ethanol-ether and ethanol-water having a MP. of 1885-1895 C.

A gelatino-silver chlorobromide emulsion (90 mole percent chloride) having internal sensitivity is prepared by adding to the gelatin solution prior to precipitation groups containing from to 12 carbon atoms; R is an alkylene group having from 1 to 15 carbon atoms; and Q is a sulfur atom, an oxygen atom or a nitrogen atom;

10.7 mg. of potassium hexachloroiridate per silver mole. 5 (B) bis'triazofium Salts represented by the formula: After washing, the emulsion is fogged to maximum denq sity by adding 100 mg. of thiourea dioxide per silver T mole. The emulsions are then coated on a film support IL J R0 1 t I at 350 mg. of silver/ft. and 260 mg. gelatin/ft To sepa- N N rate portions of the emulsion are added the addenda as 1 described in the following table. The coated samples are then exposed on an Eastman 1B Sensitometer and develwherein R R and R are as mentioned above and oped 1n Kodalith Fllm Processor Model 324 using a de- R6 and 7 are each an l r aralkyl group of from veloper having the following composition: 5 to 12 carbon atoms and C) 3-hydroxy-1,4-d1phenylpseudo-1,2,4-tr1azole. gi folrfimaldehyde blsulfite 2. A process according to claim 1 wherein said triai 1.11m te 5 zolium salt is a bis-triazolium salt.

3 3. A process according to claim 1 wherein said tria- HY f f 1 zolium salt is 1,10-dithiadecamethylene bis-3-(1,4-diphenai broml e "a yl-1,2,4-triazolium paratoluene sulfonate). S0 mm car onateli(monohy rate) 4. A process according to claim 1 wherein said triavgter tosmake 1 zolium salt is 3,3(N,N-decamethylene-dianilino)bis(1,4- P of diphenyl-1,2,4-triazolium)tosylate.

The photographic results are summarized in the follow- 5. In a fogged, direct-positive, silver halide emulsion, ing table: the improvement comprising from about 1x10 mole Development time of- 1% 1% 2% Com ound (g. m.) Rel- Rel- Relative ative y D nn. speed 7 D inspeed 7 Drain.

triazolium paratoluene sulfonate) It can be seen from the above table that Compound B to about 1X10 mole of a triazlolium salt per mole of is more eifective in controlling Dmin, than previously known compounds, i.e., Compound A.

Similar results can be obtained when 3,3'(N,N-decamethylene-dianilino)bis(1,4-diphenyl 1,2,4 triazolium) tosylate is added to the emulsion before processing or added to the developer composition to be used to process the direct-positive element. Inner salts of triazolium compounds, such as 3-hydroxy-1,4-diphenyl-pseudo-1,2,4- triazole, can also be used to provide improved photographic properties in the fogged, direct-positive emulsion prepared by the above procedure.

Although the invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, variations and modifications can be efiected Within the spirit and scope of this invention.

I claim:

1. In a process of developing an imagewise exposed direct-positive photographic element comprising a support having thereon at least one layer containing fogged silver halide grains which process comprises developing said exposed element in a silver halide composition compris ing at least 0.5 g./liter of halide ions, the improvement which comprises the presence during the development step of from about 1 l0 mole to about 1X10 mole of a triazolium salt per mole of silver; said triazolium salt being selected from the group consisting of:

(A) bis-triazolium salts represented by the formula:

wherein R R R and R are alkyl groups having from 1 to 10 carbon atoms or are aryl or aralkyl silver; said triazolium salt being selected from the group consisting of: r

(A) bis-triazolium salts represented by the formula:

wherein R R R and R are alkyl groups having from 1 to 10 carbon atoms or are aryl or aralkyl groups containing from 5 to 12 carbon atoms; R is an alkylene group having from 1 to 15 carbon atoms; and Q is a sulfur atom, an oxygen atom or a nitrogen atom;

(B) bis-triazolium salts represented by the formula:

o i i a triazolium salt per mole of silver; said triazolium salt being selected from the group consisting of:

(A) bis-triazolium salts represented by the formula:

wherein R R and R are as mentioned above and R and R are each an aryl or aralkyl group of from 5 to 12 carbon atoms; and (C) inner triazolium salts.

8. A direct-positive element according to claim 7 wherein said triazolium salt is a bis-triazolium salt.

9. A direct-positive element according to claim 7 Wherein said triazolium salt is 1,10-dithiadecamethylene bis-3- (1,4-diphenyl-1,2,4-triazolium paratoluene sulfonate).

10. A direct-positive element according to claim 7 wherein said triazolium salt is 3,3'(N,N'-decamethylenedianilino bis( 1,4-diphenyl-1,2,4-triazolium tosylate.

11. A direct-positive element according to claim 7 wherein said silver halide has been reduction and gold fogged.

References Cited UNITED STATES PATENTS 3,178,282 4/1965 Luckey et al. 9664 X 2,444,605 7/ 1948 Heimbach et al. 96-109 2,131,038 9/1938 Brooker et al. 96109 3,3 64,028 1/1968 Knig 96109 3,420,664 1/1969' Dersch et al. 96109 X 3,615,616 10/1971 Willems et al. 96-109 J. TRAVIS BROWN, Primary Examiner W. H. LOUIE, IR., Assistant Examiner US. Cl. X.R.

96109 R, 66.5 R, 108 R mg I I UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, .3,7 +0,226 Dated June 19., 1973 Inventor(s) I Glen Marshall Dappen Itis certified that error appears in the above-identified patent and that saidletters Patent are hereby corrected as shown below:

F Column 6, line 69 (claim 5) (C) inner triazolium salts" should be --3hydroXy-l, I-diphenyl-pseudo-l,2, 1 -triazole--;

Column 7, line 26, (claim '7 (C) inner triazolium salts" should be --,3-hydroXy-l, -diphenyl-pseudo-l,2, ItriaZole--.

Signed and sealed this 13th day of August 197E.

(SEAL) 'Attest:

MCCOY M. GIBSON, JR. Attesting Officer 0. MARSHA L DANN Commissioner of Patents 

